New device helps users 'hear' with their tongue

That old expression "You're putting words in my mouth!" could never really be taken literally. Until now.

Engineers at Colorado State University have been working on a way to hear with your tongue, and it might just be the biggest breakthrough for hearing since the cochlear implant.

New studies have uncovered technology
that can enable people to 'hear' with
their tongues.

A team in the Department of Mechanical Engineering, led by associate professor John Williams, has developed a hearing device that bypasses the ear and uses the mouth instead. The Bluetooth-enabled earpiece detects sound and sends electrical impulses to a retainer-like device in the mouth, which is loaded with electrodes. Just by pressing their tongue against it, wearers are able to “hear."

The idea came about in part because Williams knew it is possible to train the brain to receive info from another source, a technique known as sensory substitution. American Sign Language and Braille are two examples of sensory substitution that have worked very well, so there was already past precedent. And electrotactile stimulation as a means of sensory substitution, which is how the CSU device works, has been studied as far back as the 1960s.

Advantages of the device

The CSU device has some important advantages over the cochlear implant. First, it is simpler than surgery for cochlear implants, which involves implantation of a receiver near the auditory nerve. With surgery, not only is there a risk of damage to the sensory cells that transmit sound to the auditory nerve, but other risks include infection, injury to the facial nerve or possible rejection of the implant. Also, the new device is less expensive than cochlear implants, which cost upward of $100,000 when all is said and done.

Another advantage the CSU device has over cochlear implants is that cochlear implants are not a viable option for many of those with hearing loss. They tend to work best on the very young, and require most of the auditory system to be intact in order to function. The CSU device, on the other hand, has greater potential for widespread use.

One appealing factor about the new CSU device is its simplicity. To illustrate that, let’s compare how cochlear implants work to how the new CSU device works. Cochlear implants use an external microphone to send sound to a speech processor. After analyzing the sound, the speech processor sends the sound to a receiver, which has been surgically implanted near the auditory nerve. The receiver converts the sound into electrical impulses which are then sent to the auditory nerve. With training, the brain learns to recognize these electrical impulses as useable sound information.

Bluetooth helps users 'hear'

The device being developed at CSU, on the other hand, uses Bluetooth technology to send the electrical impulses to a small retainer-like device held in the mouth. When the user presses their tongue against the device they feel a tingling or vibrating sensation, which, with training, can enable the brain to interpret certain patterns as words. Thus, just like other forms of sensory substitution such as Braille and ASL, the user can learn to “hear."

The reason it works is that there are thousands of nerves in the tongue, and the part of the brain that interprets touch signals from the tongue is highly capable of decoding complex information. So, it becomes another form of sensory substitution.

Like previous forms of sensory substitution, the new device uses the brain’s neural plasticity to its advantage. In other words, the brain is able to form new neural connections and to make adjustments in response to new situations, even in adulthood. Fortunately this adaptability extends to learning new forms of communication as well.

Although the prototypes have been built and extensively tested, there are still improvements yet to be made. For example, the researchers have partnered with Leslie Stone-Roy, assistant professor in the College of Veterinary Medicine and Biomedical Sciences, to map the nerves on the tongue in an effort to determine the best placement of the electrodes in the retainer. The ultimate goal is twofold: to find out which areas of the tongue best detect the electrical impulses, and to determine whether those areas are identical for every person.

Results prove important to cost

The results of the findings are crucial to one of the goals of the project, which is to keep the cost of the device down. If the nerve patterns are the same from person to person, that would allow for the technology to be standardized and thus less expensive to manufacture. On the other hand, if the nerve patterns vary from person to person then each device would have to be custom made, and tailored to the individual. And of course, that would increase the cost.

With a provisional patent pending, Williams and his team are hopeful for a positive outcome. “Cochlear implants are very effective and have transformed many lives, but not everyone is a candidate,” Williams said. “We think our device will be just as effective but will work for many more people and cost less.”